Sen. Jeff Flake drew a dramatic new line against President Donald Trump and his fellow Republicans on Wednesday, promising to vote against new federal judges unless the Senate protects Special Counsel Robert Mueller's probe.

Flake, a lame-duck Arizona Republican, could jeopardize dozens of judicial nominations Senate GOP leaders want to push through before the current Congress ends in early January.

Flake, a member of the Senate Judiciary Committee who leaves office in January, offered a swift response of his own.

"Because (the legislation) has failed today, Sen. Coons and I are prepared to raise it again and again, until there is a vote on this vital bipartisan legislation on the Senate floor," Flake said on the floor. "I have informed the majority leader that I will not vote to advance any of the 21 judicial nominees pending in the Judiciary Committee, or vote to confirm the 32 judges awaiting a confirmation vote on the floor, until (the bill) is brought to the full Senate for a vote."

Other Republicans, such as U.S. Sen. Lindsey Graham of South Carolina, who is a cosponsor to the Flake-Coons bill, have said they don't think any protection for Mueller's investigation is needed.

Flake to block judicial confirmations

Flake's move puts him in a now-familiar position of battling Trump's agenda, but throws down his most serious threat. Earlier this year, Flake withheld support from approving circuit judges in a dispute with the White House over tariffs.

Without Flake's support now, Republicans would need Democratic help to pass any nominee out of the Judiciary Committee by the usual process, which seems unlikely.

For nominees who have already made it out of the committee, Flake's opposition means the GOP can't afford any other Republicans to vote against confirmation without needing Democratic support.

"I think the senator has a lot of leverage here," said Carl Tobias, a constitutional law professor at the University of Richmond. Trump and Republicans have touted their aggressive confirmation of federal judges as perhaps their most consequential action, Tobias said.

"That's going to come to a crashing halt if Flake holds out," he said.

In August 2009, Rep. Jeff Flake spent a week of his August break from Capitol Hill living a primitive, Gilligan's Island-style existence by himself on Jabonwod, Marshall Islands, a remote island in the middle of the Pacific Ocean. Here he is with a big-eyed bream. Special for The Republic

Sens. John McCain and Jeff Flake address members of the media at McCain's Phoenix office on May 28, 2014, following the release of a report stating by the Veterans Affairs that at least 1,700 veterans at the medical center were not registered on the proper waiting list, putting them at risk in the convoluted scheduling process. Charlie Leight/The Republic

Sen. Jeff Flake, in a 2015 photo, helped block an Obama-era rule protecting the privacy of Internet consumers. Flake, R-Ariz., has characterized the rule as a power grab by the Federal Communications Commission. Tom Tingle/The Republic

U.S. Sens. John McCain (right) and Jeff Flake talk with the press after their roundtable discussion with President Obama at the Carl T. Hayden VA Medical Center in Phoenix on March 13, 2015. Mark Henle/The Republic

Flake locking horns with Trump again

There are 14 nominees, for example, on the Judiciary Committee's schedule Thursday. Five of those positions are circuit judgeships, positions that are considered especially critical because most federal cases never make it past their appeals court.

Two of the five circuit nominees are in the San Francisco-based 9th U.S. Circuit Court of Appeals, which has jurisdiction over Arizona's federal cases, Tobias said.